Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$119.48	7.490%	$128.4291	$128.43	$128.45	$128.40
Purchase #2	$67.87	10.192%	$74.7873	$74.79	$74.80	$74.80
Purchase #3	$42.57	7.665%	$45.833	$45.83	$45.85	$45.80
Purchase #4	$64.72	7.415%	$69.519	$69.52	$69.50	$69.50
Purchase #5	$9.45	7.597%	$10.1679	$10.17	$10.15	$10.20
Purchase #6	$75.78	9.200%	$82.7518	$82.75	$82.75	$82.80
Purchase #7	$88.61	8.184%	$95.8618	$95.86	$95.85	$95.90
7 purchase totals =	$468.48		$507.3499	$507.35	$507.35	$507.40